A cartridge valve assembly or, more generally, a valve assembly having the control mechanism received in a separate housing, i.e. a housing separate from the valve body into which the assembly is inserted, is described in German Open Application DE-OS 33 39 464.
In this known mixing valve, the bottom of the separate housing, i.e. the housing intrinsic to the assembly or cartridge, has two inlet openings for cold and hot water and one outlet opening for the mixed water. Cylindrical walls define these openings and are provided with hose-like or tubular seals which, on the one hand, abut a face of the valve seat disk turned toward the supply in the valve body and, on the other hand, engage in recesses in the valve body of the sanitary fixture to seal against the valve body.
When the valve is pressurized by hot and/or cold water under pressure from the supply, there is a slight axial displacement of the valve disk stack in the direction of the valve actuating member. As a result, a gap can be formed between the bottom part of the separate housing and the valve seat disk.
Because of this gap between the bottom of the housing and the valve seat disk, the radial force setting the hose-like seals is significantly reduced so that, upon the development of a pressure impulse, e.g. water hammer, in the water supply line, the sealing ring can be pressed into the gap. This results in a loss of sealing effectiveness and, obviously, a danger of deterioration or destruction of the seal.